700
FXUS63 KDMX 040811
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
311 AM CDT Fri Sep 4 2026

.KEY MESSAGES...

- Low potential (20%) for isolated showers and thunderstorms in
  northeast Iowa later this morning to afternoon.

- Heat and humidity continues into this weekend. The Heat
  Advisory has been expanded another row of counties in north
  central Iowa. The heat headlines are in effect through
  Saturday.

- Low storm chances (10%) Saturday morning to afternoon in
  western Iowa. On and off storm chances continue into early
  next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 311 AM CDT Fri Sep 4 2026

Dry but warm conditions keep hold early this morning across Central
Iowa, with partly to mostly cloudy skies as temperatures as of 2am
sit through the 70s, paired with dewpoints in the upper 60s to low
70s. Broad mid to upper level ridging remains the primary feature
overhead, which is largely draped across the central to eastern
CONUS. Within the apex of this ridge is a shortwave trough that is
over the Upper Midwest region, with an area of strong 925mb
frontogenesis paired with notable upper level divergence across
Wisconsin through Central Minnesota, which has led to ongoing strong
to severe storms over these areas. Through the rest of this morning
and into the afternoon, the expectation is that this shortwave will
track eastward, with lingering shower and storm activity expected to
continue southeast with time. While most of this activity should
remain north and east out of Iowa, there is remaining potential
(20%) near sunrise to see storm development into northeast Iowa.
Weak forcing however overhead and low level dry air however will
likely keep storm development, if any, more isolated and short lived
later this morning and even into early afternoon. Cannot rule out
gusty winds though given the aforementioned dry low levels as any
storms collapse, though the concern for severe weather continues to
decrease. Outside of the low storm potential, the main weather story
continues to be the late summertime heat and humidity, thanks to the
nearby heat dome that continues to dominate over much of the
country. Forecast highs are on track to reach into the low to mid
90s this afternoon, with heat indices up to 100-105 most likely over
southern to central Iowa, but also trending even further north to
include much of north-central Iowa as well given latest trends.
Therefore, have included another row of counties (Sac to Black
Hawk) in north-central Iowa in a Heat Advisory this afternoon
through Saturday.

The start of the weekend will see little change in the overall
synoptic pattern, with the ridge building northward slightly. A
strengthened low level jet is anticipated to point due north across
Kansas through the Dakotas, where morning convection per CAMs is
anticipated to occur. Trends keep this activity mainly west of Iowa,
but some members suggest some storms making it into western Iowa
into the late morning to afternoon. If storms can develop, a
favorable environment featuring instability values around 3000-4000
J/kg and lapse rates around 7.5 C/km could lead to potential
isolated severe weather, though given lack of forcing overhead and
weak shear, the chances are quite low (10%). Will continue to
monitor trends and adjust accordingly. Otherwise, dry conditions
should generally prevail Saturday, with forecast highs again in the
low to mid 90s and heat indices up to 100-105 degrees into the
afternoon. Heat headlines therefore continue through this timeframe
as well.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 211 PM CDT Thu Sep 3 2026

A more robust trough will move east across the northern US from
Sunday into early next week. This will renew the periodic scattered
thunderstorms chances each day while also helping to squash the
thermal ridge. We will not see substantial cooling, however
temperatures Sunday into early next week should be at least a
few degrees cooler than what we have seen this week. The ridge
does look to rebuild for the middle to end of next week. Heat
and humidity along with continued scattered thunderstorm chances
looks to be the story for at least another week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1052 PM CDT Thu Sep 3 2026

Main change this issuance was introducing LLWS to more sites
tonight, which will range between 35 and 40kts. Have delayed
rain at KMCW in the Prob30 group. Most of this activity will
remain north of the site. There is <10% chance of thunderstorm
development after 20z, highest confidence at KALO, but could
also affect KMCW and KDSM. Will continue to monitor trends.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 1 PM this afternoon to 7 PM CDT Saturday
for IAZ033>039-044>050.
Heat Advisory until 7 PM CDT Saturday for IAZ057>062-070>075-
081>086-092>097.

&&

$$

SHORT TERM...Bury
LONG TERM...Hagenhoff
AVIATION...Jimenez